Polyester fabric is widely used in textile material though it has some problems such as low colour value, high refractive ratio(1.62) and etc. In order to give Z-black colour of polyester fabric, this study has selected several disperse dyes by measuring of absorbance, dyed in their optimum conditions and treated with 4 kinds of low refractive compounds such as silicone, fluorine, urethane and silicone-fluorine mixed compounds. The bathochromic effect of treated PET fabric evaluated as lightness(L) change by uv-visible spectrophotometer. This study also investigated that the effect of used bathochromic agents on the washing and lightfastness of treated PET fabric.